Inorganic arsenic excretion

Human volunteers who drank wine containing inorganic arsenic excreted methylarsonic and cacodylic acids in their urine (96). These two compounds also occur in the urine of copper smelters, the elevated arsenic content presumably coming from copper ores (97). Cacodylate ion forms when H34As04 is administered orally to dogs or hamsters (98-100). A Japanese group reported that various small animals will form methylar-sonate and cacodylate from H3ASO4 (101). On the basis of presently available data, it remains uncertain whether arsenic biomethylation occurs from the bodily processes of the mammals themselves or from microflora of the intestinal tract. 

Inorganic arsenicals are oxidized in vivo, biomethylated, and usually excreted rapidly in the urine, but organoarsenicals are usually not subject to similar transformations. 

Charbonneau, S.M., K. Spencer, F. Bryce, and E. Sandi. 1978. Arsenic excretion by monkeys dosed with arsenic-containing fish or with inorganic arsenic. Bull. Environ. Contam. Toxicol. 20 470-477. 

Buchet, J.P., Lauwerys, R. and Roels, H. (1981b) Urinary excretion of inorganic arsenic and its metabolites after repeated ingestion of sodium metaarsenite by volunteers. International Archives of Occupational and Environmental Health, 48(2), 111-18. 

Inorganic arsenic is eliminated primarily via the kidneys in humans as well as laboratory animals. Studies in adult human males voluntarily ingesting a known amount of either As(III) or As(V) indicate that 45-75 % of the dose is excreted in the urine within a few days to a week (Pomroy et al., 1980 Tam, Char-bonneau and Bryce, 1979 Buchet, Lauwerys and Roels, 1981a Buchet, Lauwerys and Roels, 1981b Lee, 1999). Relatively few studies in volunteers have included the measurement of arsenic in both feces and urine. However, Pomroy et al. (1980) reported that 6% of a single oral dose of arsenic acid was excreted in the feces over a period of seven days compared to 62 % of the dose excreted in urine. No quantitative data are available that directly assess the significance of biliary excretion of As(III) or As(V) in humans. 

Hakala, E. and Pyy, L. (1995) Assessment of exposure to inorganic arsenic by determining the arsenic species excreted in urine. Toxicology Letters, 77(1-3), 249-58. 

Kenyon, E.M., Del Razo, L.M. and Hughes, M.F. (2005a) Tissue distribution and urinary excretion of inorganic arsenic and its methylated metabolites in mice following acute oral administration of arsenate. Toxicological Sciences, 85(1), 468-75. 

Offergelt, J.A., Roels, H., Buchet, J.P. et al. (1992) Relation between airborne arsenic trioxide and urinary excretion of inorganic arsenic and its methylated metabolites. British Journal of Industrial Medicine, 49(6), 387-93. 

Vahter, M., Friberg, L. and Rahnster, B. (1986) Airborne arsenic and urinary excretion of metabolites of inorganic arsenic among smelter workers. International Archives of Occupational and Environmental Health, 57(2), 79-91. 

Although trivalent inorganic arsenic, with its propensity for binding to the SH group of enzymes, is acknowledged to be more toxic to humans than pentavalent inorganic arsenic, it must be recognized that As can be converted to As in the human body as part of the reduction/biomethylation pathway of excretion... 

Telolahy, P., Morel, G., Cluet, J.L., Yang, H.M., Thieffiy, N., deCeaurriz, J. (1995). An attempt to explain interindividual variability in 24-h urinary excretion of inorganic arsenic metabolites by C57 BL/6J mice. Toxicology 103 105-12. 

Mammals, including humans, detoxify inorganic arsenic by methylation, yielding cacodylic acid (dimethylarsinic acid) as the chief urinary excretion product. Disposition by urinary excretion is usually prompt. Elimination of the arsonic acid (monomethyl) compounds has not been extensively studied, but urinary excretion of the unaltered compound and/or a further methylated form would seem likely. 

Arsenobetaine, arsenosugars and arsenocholine are organoarsenicals less toxic for animals and humans than inorganic arsenic compounds, and have been found in certain marine organisms and in seafoods. They are excreted rapidly in urine (about 70% of the dose in 24h) . Natural arsenic is a pure one-isotope element ( As) and had to be labelled with radioactive arsenic for metabolic studies. As has been chosen as the most suitable isotope for tracer investigations. 

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